A day after he received confirmation from the Senate, Eric Fanning was sworn in Wednesday as Secretary of the Army, becoming the first openly gay leader of any U.S. military service.

The event served as another milestone for the Obama administration, which has long been supporting the rights of the LGBT community, NBC News reports.

"It has been a long process to get here, one that I don't think even the writers from 'House of Cards' could have scripted if they tried," Fanning said after he was sworn in by Defense Secretary Ashton Carter.

He called his appointment "a tremendous honour."

Carter said Fanning "embodies the kind of strong and steady leadership and civilian commitment to our men and women in uniform that have made our military the finest fighting force the world has ever known."

Fanning's nomination had been stalled since President Barack Obama picked him as acting secretary of the U.S. Army last November.

His confirmation on Tuesday comes five years after the repeal of the "don't ask, don't tell" policy in the U.S. military which barred gays from being open about their sexuality, according to NBC News.

Human Rights Campaign president Chad Griffin called Fanning's confirmation "a demonstration of the continued progress towards fairness and equality in our nation's armed forces."

Before his appointment as Army secretary, Fanning served as acting undersecretary of the Army and chief management officer. He also served as secretary of the Army's senior civilian assistant and principal adviser on matters related to the management and operation of the Army, including development and integration of the Army Program and Budget.

He also worked as Special Assistant to the Secretary and Deputy Secretary of Defense. He was the acting secretary of the U.S. Air Force in 2013.

"I'm honoured by today's Senate confirmation and thrilled to return to lead the total Army team," Fanning said.

His confirmation came after Republican Sen. Pat Roberts dropped his opposition over plans by the Obama administration to close the prison facility at Guantanamo Bay, Cuba and transfer prisoners to the U.S.

Roberts said he was assured by the administration that time has run out to transfer the detainees to Kansas.

Democratic Rep. Nancy Pelosi posted on Twitter that Fanning is "capable, experienced & will lead with honor!"

Republican Sen. Dan Sullivan said he "appreciated (Fanning's) recognition of Alaska's strategic importance & need for larger @USArmy."

Last month, Roberts clarified that "as a veteran, a Marine — I support Mr. Eric Fanning for this post. If the White House calls and assures me that terrorists held at Guantanamo will not come to Fort Leavenworth, I will release the hold — immediately."

The issue was based on Obama's announcement to close the Guantanamo prison facility. It is considering 13 locations in the U.S. including seven prison facilities in Colorado, South Carolina and Kansas and six sites on current military bases.

In March, Roberts introduced a Senate resolution to reject any plan to transfer the detainees to the U.S.

Before the vote, Roberts said, Fanning "will be a tremendous leader as Army secretary and will do great by our soldiers at Fort Leavenworth and Fort Riley."